After observing that the performance values of ST-Retrieval were higher than those of the search engines,we tested the statistical significance of the results using the non-parametric Wilcoxon Signed
Rank Test [1]} with a significance level \(\alpha =0.05\) .
We stated the null hypothesis (\(H1_0\) ) as: “The metric values
from ST-Retrieval are equal to those
from other search engines". The alternative hypothesis (\(H1_1\) ) states that there is a difference between these metrics. Table REF  shows the p-values obtained for each metric (treatment) reported in Table
REF  after running the tests. With the exception of the number of hits at first position (H@1), all p-value values are less than 0.05. This means that we can reject \(H1_0\)  for all the metrics (except H@1), and conclude that the differences between ST-Retrieval and the existing search engines are statistically significant. Finally, we successfully answer RQ#1 by saying that ST-Retrieval does improve the search results.
<TABLE>